Pour 1 ml of sodium hydroxide into a test tube, add 1-2 drops of phenolphthalein and add 1-2 ml

Pour 1 ml of sodium hydroxide into a test tube, add 1-2 drops of phenolphthalein and add 1-2 ml of sulfuric acid solution until the color disappears. Write the equations in molecular, full, and abbreviated ionic form.

Sodium hydroxide is a soluble base, an alkali that can change the color of indicators.

Phenolphthalein is colorless in a neutral medium.

When added to alkali, its color changes to crimson. After adding a few drops to the alkali of sulfuric acid, the color of phenolphthalein disappears, since the medium again becomes neutral, salt (sodium sulfate) and water are formed.

2 NaOH + H₂SO₄ = Na₂SO₄ + H₂O.

2 Na¹⁺ + 2 OH^1- + 2 H¹⁺ +SO₄^2- = 2 Na¹⁺ + SO₄^2- + H₂O.

2 H¹⁺ + 2 OH^1- =  H₂O.